This invention relates in general to drive train systems for transferring rotational power from a source of rotational power to a rotatably driven mechanism. In particular, this invention relates to an improved driveshaft assembly for use in such a drive train system that is axially collapsible in the event of a collision to absorb energy and a method for manufacturing same.
Torque transmitting shafts are widely used for transferring rotational power from a source of rotational power to a rotatably driven mechanism. For example, in most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical vehicular drive train system includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of misalignment between the rotational axes of these three shafts.
A recent trend in the development of passenger, sport utility, pickup truck, and other vehicles has been to design the various components of the vehicle in such a manner as to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle. As a part of this trend, it is known to design the drive train systems of vehicles so as to be axially collapsible so as to absorb energy during a collision. To accomplish this, the driveshaft tube may be formed as an assembly of first and second driveshaft sections that are connected together for concurrent rotational movement during normal operation, yet are capable of moving axially relative to one another when a relatively large axially compressive force is applied thereto, such as can occur during a collision. A variety of such axially collapsible driveshaft assemblies are known in the art.
It has been found to be desirable to design axially collapsible driveshaft assemblies of this general type such that a predetermined amount of force is required to initiate the relative axial movement between the two driveshaft sections. It has further been found to be desirable to design these axially collapsible driveshaft assemblies such that a predetermined amount of force (constant in some instances, varying in others) is required to maintain the relative axial movement between the two driveshaft sections. However, it has been found that the manufacture of such axially collapsible driveshaft assemblies is somewhat difficult and expensive to manufacture than convention non-collapsible driveshafts. Thus, it would be desirable to provide an improved method of manufacturing a driveshaft assembly for use in a drive train system that is relatively simple and inexpensive to perform.
This invention relates to an improved driveshaft assembly for use in a drive train system that is axially collapsible in the event of a collision to absorb energy and a method for manufacturing same. Initially, an end of a first tube is disposed within a forming die having a die cavity that defines a non-circular cross sectional shape. Then, the end of the first tube is expanded outwardly into conformance with the die cavity, such as by mechanical deformation, electromagnetic pulse forming, hydroforming, and the like. As a result of this expansion, the end of the outer tube is deformed to have the same cross sectional shape as the die cavity, including a plurality of outwardly extending regions and a plurality of inwardly extending regions. Following this expansion, an end of a second tube is inserted within the deformed end of the first tube. Next, the end of the second tube is expanded outwardly into conformance with the end of the first tube, such as by mechanical deformation, electromagnetic pulse forming, hydroforming, and the like. As a result of this expansion, the end of the second tube is also formed having the same non-circular cross sectional shape including a plurality of outwardly extending regions and a plurality of inwardly extending regions. The outwardly extending regions and the inwardly extending regions of the second tube extend into cooperation with the outwardly extending regions and the inwardly extending regions of the first tube, respectively, so as to cause the first and second tubes to function as cooperating male and female splined members. As a result, a rotational driving connection therebetween to form the driveshaft. When a relatively large axial force is applied to the ends of the telescoping driveshaft, the second tube will move axially within the first tube, thereby collapsing and absorbing energy.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.